Terahertz (THz) devices are designed to operate from 0.1-10 THz. The THz spectrum has unique properties such as penetration through soft materials and reflecting from hard materials, which make THz technology a prime candidate for imaging. Plasmons are longitudinal charge oscillations in carrier rich materials. Plasmons can be excited in transistors and can induce a DC voltage between the source-drain when certain necessary conditions are satisfied. U.S. Pat. No. 9,105,791 and CN 104916732A describe THz devices.